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How to charge AC with propane?

The old R22 window AC that I filled with R134a is still running great, but it's time to try something new. So I bought R290 refrigerant (propane) to fill the system with. Yes, I know that it's flammable, so please don't go there. My question is what pressure do I fill it to? Or would I be better off just charging it in very small amounts with a thermometer in the vent and once the temp starts to go up, take a little out so it's the coldest? Thanks.

Re: How to charge AC with propane?

So I put in one 8 ounce can, and the low side pressure is around 55 PSI, and the vent temp is 48 degrees with an ambient temp of around 73, so the air temp is dropping about 25 degrees as it goes over the evaporator. The system originally took 13.6 ounces of R22, so how much propane would it need? I thought it took 42% of the original charge, so just under 6 ounces. However, the pressure still seems low after putting 8 ounces in. I don’t have a piercing valve on the discharge tube so I can’t measure head pressure, but I can install one if it would help.

Re: How to charge AC with propane?

Thanks for your help. I bought a piercing valve to put on the tube coming out of the compressor so I can check head pressure too. I’ll report back when I have time to install the valve and get a head pressure reading.

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Re: How to charge AC with propane?

Because hydrocarbon compressors have different sized pistons and cylinders as the gas needs to be pumped at a different rate from non-hydrocarbon fluids.
[Edit] The above is a rather generalised statement aimed towards the smaller compressors.

Re: How to charge AC with propane?

.

I agree with Brian.

As a toy and a test piece it is OK but I would
not choose to do it my self for the reasons Brian said
I know you only put 8 ounces of the stuff inside it but
the other reason I would not do it is the electrics on
the Compressor, motor, stat and other switches are
not rated for flammables and it might cause an issue
if the thing was ever to leak.

Re: How to charge AC with propane?

Originally Posted by martinw58

i thought you charged to super heat on capilery systems and sub cooling on txv systems without a receiver

I would say both, so you know it’s not banking up in condenser.
Room would also be close to or in range of set point so stable conditions.
Propane to me same as R22 on P/T chart, just don’t need as much propane in system, as previously mentioned.

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